TIPPECANOE COUNTY – Three Purdue engineering students face a series of felony charges after prosecutors say they engaged in a scheme to alter their own grades.

According to court documents, Purdue’s Information Technology Security Services for Purdue University (ITaP) contacted campus police after learning that a student was logging into a professor’s university computer account and changing grades.

That professor had contacted the department twice to reset his password, saying that someone had changed his password.

Computer security analysts looked at the logs and discovered that someone had accessed the professor’s account using an IP address that wasn’t affiliated with the university and changed the password. That happened on two occasions: once on Nov. 30, 2012, and another time on Dec. 18, 2012.

ITaP traced the second incident to Mitsutoshi Shirasaki, a 24-year-old Purdue student who prosecutors said logged onto Purdue’s Air Link wireless network, using the professor’s account to change his grade from a C to a B.

Investigators later discovered that Shirasaki changed grades in four other classes that semester. Prosecutors said he used the same tactic to access other professors’ computer accounts so he could change his grades.

Further investigation uncovered that the student’s activities went back to 2010, and that he had changed more than a dozen of his grades. In some cases, Shirasaki made a slight change, elevating a C to B or D to a B+. In most other cases, according to court documents, he changed his grade from a failing mark to an A. On one occasion, prosecutors said, he changed the grade of his girlfriend, elevating her from an A to an A+ in a class.

Shirasaki’s instructors confirmed to investigators that the grades had been altered without their permission.

According to court documents, Shirasaki installed key-logging devices in keyboards, swapping them with keyboards inside classrooms and professors’ offices. He picked locks to get into the offices, court documents said. Investigators found several keyboards that had been tampered with.

Shirasaki’s girlfriend informed investigators that he’d told her about the plot to change grades and also dumped keyboards and his computer out in a field after he realized police were onto him. His girlfriend said two other students, Sujay Sharma, 24, and Roy Chaoran Sun, 24, helped Shirasaki pull off the scheme.

Court documents said both Sharma and Sun helped Shirasaki break into offices by serving as lookouts. All three students gained access to tests before taking exams, court documents said.

Shirasaki said Sun taught him how to alter the keyboards to install key-loggers. On one occasion, Shirasaki said Sun changed a grade for him while he was away from school with his family, court documents said.

The three face several charges ranging from conspiracy to commit computer tampering and computer trespass to burglary, theft and receiving stolen property. All are felonies.